1. Field of the Invention
The present invention relates to an insulation-displacement terminal fitting and to a method for producing the same.
2. Description of the Related Art
A known insulation-displacement terminal fitting is disclosed in Japanese Unexamined Patent Publication No. 8-241740. This terminal fitting includes inward facing blades formed on a pair of side walls. The blades are formed by embossing portions of the side walls inwardly to project in V-shape when viewed in a direction in which a wire is pushed. A resin coating of a wire pushed between the blades is cut by the edges of the V-shaped blades and a core of the wire then contacts the projecting ends of the blades.
Insulation displacement terminal fittings with blades that project inwardly from side walls, including the terminal fitting disclosed in JP 8-241740, have a pair of V-shaped edges that are inclined to approach each other in a wire pushing direction to guide a wire into a proper position between the blades. A smaller angle between the inclinations of the V-shaped edges and the wire pushing direction provides a better guiding function because the wire is less likely to get caught. However, if this angle is too small, the wire may merely be deformed elastically as it is pushed between contact edges of the blade portions without the resin coating of the wire being cut. Thus, the blade portions and a core of the wire may not contact each other.
In view of the above, an object of the present invention is to securely cut a resin coating of a wire without impairing a function of guiding the wire to between blades.
The invention is directed to an insulation displacement terminal fitting with a pair of side walls and at least one pair of blades provided respectively on the side walls for connection with a wire. Each blade comprises a projecting end that acts as a contact edge, and cutting edges for cutting an insulation coating of the wire pushed between a pair of blades to bring a core of the wire into contact with the contact edge. The cutting edges are inclined to guide the wire from the side walls to the contact edge when viewed from the longitudinal direction of the wire. At least one hook edge is formed at ends of the cutting edges toward the contact edge. Preferably, the hook edge is aligned to project toward the wire being pushed between the blades According to a preferred embodiment, the blades are formed to project in a substantially V-shape when viewed in a pushing direction of the wire by bending or embossing portions of the side walls inwardly. Most preferably, the cutting edges are substantially V-shaped.
The hook edges are formed at the ends of the V-shaped edges toward the contact edges and project toward the wire. Thus, the resin coating of the wire can be cut securely by the hook edges even if the angle of inclination of the V-shaped edges is made smaller to facilitate guiding of the wire. In other words, both the function of guiding the wire from the side walls toward the contact edges and the function of securely cutting the resin coating can be realized.
Preferably, each hook edge has a pointed shape of a substantially right angle or acute angle when viewed in the longitudinal direction of the wire or the longitudinal direction of the terminal fitting. The pointed shape enables the hook edges to bite into the resin coating securely and to cut it open.
Each hook edge preferably is formed to be substantially continuous and flush with the corresponding contact edge when viewed in the longitudinal direction of the wire. Thus, an embossing step to cause the hook edge to project inwardly or outwardly with respect to the contact edge is unnecessary.
Each hook edge is formed to be continuous with and arranged at an obtuse angle with respect to the cutting edges of the blades.
The side walls preferably include depressed portions or valley-shaped areas that will become the substantially V-shaped cutting edges. These depressed portions are punched or cut out to have an arcuate or trapezoidal shape before the side walls are bent. The hook edges then are formed by bending or embossing the arcuate or trapezoidal depressed portions. Since the portions which will become the hook edges are punched out to have an arcuate or trapezoidal shape, a punching die can be formed more easily as compared to a case where the hooks are punched out in V-shape.
The invention also is further directed to a method for producing an insulation displacement terminal fitting for connection with a wire. The method comprises providing a terminal material. The method then comprises shaping the terminal material to provide at least one pair of blades at side walls of the terminal fitting for connection with the wire. The method then continues by forming the blades with projecting ends that function as contact edges, and cutting edges for cutting an insulation coating of the wire pushed between the blades to bring a core of the wire into contact with the contact edges. The cutting edges are formed to be inclined to guide the wire from the side walls to the contact edges when viewed from the longitudinal direction of the wire. The method also includes forming hook edges at ends of the cuffing edges toward the contact edges.
According to a further preferred embodiment, the method further comprises punching or cutting out valley-shaped depressed edges on areas of the side walls that will become the blades. The valley-shaped depressed edges have arcuate or trapezoidal shapes before the side walls are bent. The method concludes by bending the portions of the side walls adjacent the arcuate or trapezoidal depressed edges to form the cutting edges, the hook edges and the contact edges.
These and other objects, features and advantages of the present invention will become apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings.